As people get older, changes in body composition and the loss of skeletal muscle contribute to an increased risk of developing many age-related disorders, including hypertension, diabetes, heart disease, obesity, osteoporosis, diminished muscle function, the onset of physical frailty, and the loss of an independent lifestyle. Safe and effective nutrition and exercise recommendations must be found and used for elderly people to have sufficient muscular strength, power, and function to remain physically active and functionally independent. The objective of this study is to test whether consuming a beef-containing diet, compared to consuming a meat-free (lacto-ovo vegetarian) diet, promotes increased fat-free mass, decreased body fat, increased muscle size, and increased muscle strength and power, and preserves iron status, in older men who start a strength training program. RESEARCH PLAN: Men aged 60-75 years, will participate in a strength training program for 12 weeks. All of the men will be counseled to self-select a lacto-ovo vegetarian (meat-free) diet during the study. In addition, half of the men will be provided 0.6 g proteinokg-1oday-1 from foods which contain texturized vegetable protein, and half of the men will be provided 0.6 g proteinokg-1oday-1 from beef. Thus, beef will be the only source of meat in this study and the protein provided is expected to be about 50 % of the total protein intake of all men. Before, mid-way, and at the end of the strength training period, muscle strength and power, whole body composition (fat mass and fat-free mass), whole body muscle mass, leg muscle area, muscle fiber size, muscle creatine and phospocreatine content (compounds which may promote muscle enlargement), resting metabolic rate, and iron status will be measured.